This switching regulator uses the SEPIC topology to provide a regulated output voltage that can be higher than, the same as, or lower than the input voltage, making it great for applications with widely-varying power supplies and for battery-operated applications where the battery transitions from being above the output to below the output as it discharges. The small (0.4″×0.7″) module can support input voltages from 1.5 V to 12 V, has an adjustable output from 2 V to 12 V, and can supply over 300 mA in typical applications.

These things are great for portable power on the cheap. With a built-in on/off switch, and a 6-inch cable, you can get around 6V with 4 alkaline AA batteries, or around 5V with nimh rechargeables. Note: It is not safe to use alkaline batteries if connected directly to a 5 volt microcontroller, such as the ATtiny series.